Fibre-matrix semifinished products in the context of the present invention are composites made of semifinished fibre products in which fibre materials in the form of fibres, fibre bundles or filaments provided as semifinished fibre product plies are enveloped by a protective and ply-determining thermoplastic matrix. Such fibre-matrix semifinished products are also variously referred to by the terms fibre composite, composite or organosheet.
Fibre-matrix semifinished products are produced on a large scale even today for example by Bond-Laminates GmbH, Brilon, Germany in sheet form under the name Tepex®. These fibre-matrix semifinished products in sheet form already possess all the technical properties demanded of components to be manufactured therefrom. Processing of fibre-matrix semifinished products in sheet form to afford the finished component, which is finally employed for example in motor vehicles, is effected in further process steps, in particular by forming, dividing, joining, enhancing, etc.
Textile reinforcement of a fibre-matrix semifinished product employs textile semifinished products in which a multiplicity of individual filaments are suitably interconnected. These are in particular sheetlike textile semifinished products, preferably fabrics, based on endless fibres and optionally also long fibres.
The endless fibres for use for a textile semifinished product feature high mechanical performance at low weight. These are preferably technical fibres, in particular glass or carbon fibres.
High anisotropy is a peculiarity of the textile semifinished products employed as textile reinforcement in fibre-matrix semifinished products. It is only this anisotropy, i.e. the direction-specific properties such as for example the high mass-specific strength and torsional stiffness of textile semifinished products, which allows the production of fibre-matrix semifinished products having great lightweight construction potential, particularly for use in structural and semistructural applications.
However, according to WO 2010/132335 A1 the prior art processes result in fibre-matrix semifinished products which upon closer inspection reveal a layered construction. Here, the matrix resin composition which encapsulates and embeds the textile semifinished product to form an interpenetrating network therewith differs from the surface resin composition. The latter is either free of fibre material or comprises, as in WO 2010/132 335 A1, a different polyamide.
WO 2012/132399 A1 distinguishes, within a fibre-matrix semifinished product, a surface resin composition from a matrix resin composition.
Finally EP 1923420 A1 or else WO 2012/058379 A1 describe in the example section the layered construction of composite materials from films.
However, precisely a layered construction of fibre-matrix semifinished products, also described in the further course of this application as composites or composite materials, can upon employment thereof in mechanically stressed articles of manufacture lead to delamination which is apparent for example in a reduction in flexural strength in the flexural test according to ISO178. There is also a danger of insufficient attachment or reduced attachment of the matrix polymer to the fibre material caused by additives in the matrix resin to be employed, for example flame retardant additives.
Proceeding from this prior art the problem addressed by the present invention was accordingly that of providing flame-retarded fibre-matrix semifinished products not liable to delamination in which despite the use of flame retardant additives the attachment of the matrix polymer to the fibre material is maintained, wherein the criterion for maintenance of bonding is an identical or better flexural strength and “identical” is to be understood as meaning a deviation of not more than ±3% from a reference value for a non-flame-retarded composition.